Historically, a number of sensors have been used to detect earthquakes or other large-scale displacement (e.g., movement of a structure, such as a bridge support). Seismometers can be used to measure velocity at a very high precision, and this velocity can be integrated to determine an amount of movement (displacement) over a given time frame. Similarly, an accelerometer can be used to determine acceleration with a high degree of precision, and this acceleration data can be double integrated to determine a displacement over a given time frame. More recently, global navigation satellite system (“GNSS”) technology has evolved to the point where it can be used to measure displacement of a known point.
Each of these technologies has limitations, however. Seismic sensors (e.g., seismometers, accelerometers) tend to experience drift over time; as such, while measurements over a short observation window are highly precise, measurements over longer windows are subject to such drift, creating imprecision and/or inaccuracy. Additionally, such seismic sensors are subject to clipping or saturation when detected dynamics overload sensor capabilities, preventing such sensors from measuring the full displacement in highly dynamic situations. On the other hand, GNSS technology generally cannot provide sufficient resolution to detect displacement with a high degree of precision over a short observation window.
There have been attempts to combine different types of seismic data sets in order to obtain better estimates of displacements and earthquake parameters. Such efforts, however, generally have been limited to collection of different data sets from different measurement devices and correlation of these data sets using post-processing techniques. While certainly useful for the study of earthquake behavior, such techniques necessarily include far too much latency to be of use in earthquake early warning (“EEW”) systems.
More specifically, one of the fundamental requirements of EEW systems, critical infrastructure monitoring systems, and other mission critical displacement applications is to quickly detect and process the information from a strong motion event earthquake event, i.e. event detection and location, magnitude estimation, and the peak ground motion estimation at the defined targeted site. Early warning can enable civil protection authorities to provide pre-programmed emergency response actions: Slow down or stop rapid transit trains and high-speed trains; shutoff of gas pipelines and chemical facilities; stop elevators at the nearest floor; send alarms to hospitals, schools and other civil institutions; and the like.
Thus, there is a need for an EEW that can provide more accurate, and faster data to allow more accurate assessment and earlier warning of earthquakes and other structural displacements.